Numerous drugs are known for their unpleasant taste or mouthfeel. The prior art has disclosed products to mask the taste of these drugs, but the products themselves often suffer from unpleasant tastes. Patient compliance with prescribed drug therapies is often low because of this.
The functionality and effectiveness of certain solid drugs such as ion exchange resins is dependent on the active surface area. Fine particles achieve the desired therapeutic effects more effectively than course particles because the former have a higher surface area to weight ratio, e.g., a higher active surface. For example, in the case of ion exchange resins, e.g., cholestyramine , a greater surface area allows enhanced adsorption of bile acids, increased ion exchange, as well as other surface phenomena.
While course drug particles do not have sufficient effective surface area to be as effective as finer drug particles, the finer particles suffer from certain handling, processing, and formation problems. The finer particles, having a larger total surface area than courser particles, tend to be organoleptically perceived as more bitter or astringent and too dry. These organoleptic characteristics are undesirable. Traditionally, when fine particles were added in therapeutic amounts to a delivery vehicle, e.g., a confectionery formulation, the fine particles tended to disrupt the continuous phase characteristics of the final product.
The prior art has not disclosed efforts to delay hydration of unpleasant tasting drugs. To be effective, coatings must not merely mask the taste, e.g., overcome the unpleasant taste, but also delay hydration of the drug until it passes the oral cavity. Typically, the prior art has focused on water-soluble vehicles, which do not delay hydration of the drug long enough to prevent the unpleasant taste perception.
Additionally, the prior art has not disclosed an effective way of dealing with irregular shaped drug particles, e.g., various morphological structures or surfaces having sharp corners or needlelike projections. Simple conventional mixing techniques have not been completely successful in that the coating was not uniform. Conventional fluidized bed spray coating techniques have also failed to effectively provide a uniform coating on irregular shaped particles. Drug particles which have a low bulk density in addition to being irregularly shaped are particularly hard to uniformly coat with either of these conventional coating techniques. Uniform coatings therefore have been difficult to achieve when the drug particulates had a low bulk densities irregular surfaces, or both. In addition to being uniform, the coatings must be sufficiently flexible to resist cracking during processing.
The instant invention provides a drug delivery system which uniformly coats and protects the drug from moisture and subsequent hydration prior to complete ingestion. The inventive delivery system effectively wets low bulk density drugs as well as drugs having physical structures which are difficult to uniformly coat and provides controlled release of the drug.
The invention provides a method of coating low bulk density, difficult to coat drug particulates as well as providing a coating which protects unstable drugs from destabilizing conditions.